Self-adjusting hydraulic shock absorber



April 18, 1961 H. P. DoETscH 2,980,418

sELF-ADJUsTING HYDRAULIC sHocK ABsoRBER ffllllll III ATTORNEYS.

SELF-ADJUSTING HYDRAULIC SHOCK ABSORBER The present invention relates to a self-adjusting shock absorber suitable for use with wheeled vehicles and which automatically adjusts itself to operate effectively for loads of different weights which are carried by the vehicle from time to time.

Generally the shock absorber of the present invention comprises a main cylinder and a movable cylinder which moves inwardly and outwardly of the main cylinder in response to road shocks. A reservoir for hydraulic fluid 1s provided. When the load is increased, Huid is pumped Y from the reservoir into the shock absorber system thereby increasing the mean stress applied to the resilient portion of the shock absorber. When operating at light loads,

movable cylinder reaches the terminal portion of its outward movement. Under heavy loads, however, the iiuid pumped from the reservoir is retained in order to maintain the increased stressing of the resilient portion. Under heavy loads, the limit of outward movement of the movable cylinder is reduced so that the pumped fluid is not returned to the reservoir. As soon as light loading is resumed, the travel of the movable cylinder is increased and the pumped fluid is returned through passages which remain closed for heavy loads.

Various objects, features and advantages of the invention will become apparent upon reading the following specification together with the Vaccompanying drawing forming a part hereof.

Referring to the drawing, the single figure is a side view in axial section of a shock absorber embodying the invention.

The shock absorber comprises a main outermost cylinder 1. In the top of the main or outermost cylinder 1, there is disposed a suitable resilient medium such as a compressed gas 2. The gas 2 is conned within the closed top of the outermost cylinder 1 by a freely vertically movable wall or partition 3. Below the partition 3, there is a high pressure working space 4. The upper end of an innermost or damping control cylinder 5 communicates with the working space 4. The control cylinder 5 is disposed Vwithin an intermediate stationary cylinder 6 which is fixed at its upper end to the fixed partition 7. The partition 7 constitutes the bottom wall of the workfing space 4. The lower end of the control cylinder 5 communicates with the interior S of a vertically movable cylinder 9. The movable cylinder 9 slides freely within the intermediate cylinder 6 and a packing or sealing ring 9a disposed at the lower end of the intermediate cylinder 6 engages the outer surface of the movable cylinder 9 `and prevents liquid leakage therepast during reciprocation of the movable cylinder 9.

Clamped between annular nuts 10 and 11 at the top of the movable cylinder 9 is a exible check valve and sealing member 12. The check valve member 12 has a sealingA lip which engages the controlcylinder 5 and permits'liquid within the intermediate cylinder 6 to ow freely unidirectionally into the interior 8 of movable cylinder 9, while preventing flow in the reverse direction.

2,939,413 Patented Apr. 18, 1961 Axially spaced orifices 13, 14, 15 and 16 are formed in the wall of the control cylinder 5. An aperture 17 is formed in the wall of the intermediate cylinder 6 near its upper end. A check valve 18 is disposed at the upper end of a downwardly extending refill pipe 19 which extends through the aperture 17 and communicates at its lower end with a reservoir space 20 between the outermost cylinder 1 and the intermediate cylinder 6. A packing or sealing ring 20a prevents leakage of liquid in the reservoir space 20 around the external surface of the movable cylinder 9. An orifice 21 is formed in the wall of the movable cylinder 9 near its upper or inner end and in the extended position shown in the drawing, the orifice 21 places the reservoir space 20 in communication with the upper portion of the interior 8 of the movable cylinder 9. A longitudinal groove 22 is formed in the external surface of the movable cylinder 9 near its upper end. Slightly before the movable cylinder 9 reaches the extended position shown in the drawing, the groove l the pumped fluid is returned to the reservoir when the t 22 by-passes the sealing ring 9a, temporarily placing the interior 23 of the intermediate cylinder 6 in communication with the reservoir space 20 during the terminal portion of the outward movement of the cylinder 9. A ring 24 for connection to the axle of a vehicle is provided at the lower end of the movable piston 9. A helical compression spring 25 is fixedly secured at its upper end to the outermost cylinder 1. A piston 26 provided with by-pass passages 26a is disposed at the lower end of the control cylinder 5. The piston 26 guides the movablercylinder 9 during its vertical reciprocation and restricts liquid flow between the upper and lower portions of its interior S. A ange 27 at the lower end of mov` able cylinder 9 is engageable with the lower end of compression spring 25 under maximum load conditions. A ring 28 is provided at the top of the main cylinder 1 for connection to the body of the lvehicle. A suitable hydraulic fluid completely fills the Working space 4, the interior 8 of the movable piston 9 andthe space 23 Within the intermediate cylinder 6. The reservoir space 2t) is only partially filled with the hydraulic fluid.

In operation, when the vehicle passes over a bump, the movable cylinder 9 is forced upwardly within the intermediate cylinder 6. Liquid is forced up through the control cylinder 5 into the working space 4, thereby moving the partition 3 upwardly and increasing the pressure of the compressed gas 2. Liquid also enters the con* trol cylinder 5 through the metering orifices 14, 15 and 16. If the cylinder 9 moves to the limit of its upward or inward travel, so that the annular nut 10 abuts the wall 7, the return movement is produced by the action of the compressed gas 2 and the speed of return movement is controlled in part by the flow-restricting action of the piston 26 with its by-pass passages 26a. During the initial portion of the return stroke, liquid below the check valve 12 may enter the interior of control cylinder 5 through the metering orifices 14, 15 and 16. However, as the return movement proceeds, the metering orifices are successively shut off from communication with the upper portion of the space 8 above the fixed piston 26 and during the final portion of the return stroke, all liquid flow must take place through the by-pass passages 26a of the piston 26. The damping or retarding action is thus progressively increased as the downward return movement of cylinder 9 proceeds. During this return movement, the action of check valve 12 creates a suction which causes liquid to be drawn upwardly through the refill pipe 19 and check valve 18 from the reservoir space 20 so that the interior of the intermediate cylinder 6 is maintained filled.

mediate cylinder `6 increases the total volume of liquid which is presentrin the system 4-5-8423'and thus increases the pressure which isapplied to the compressed gas 2 during upward movement of the cylinder 9.` `for a Vlight or normal load, the pressure applied to theliquid in the system 44-58Y--Z'V-bythe compressed gas 2-will cause liquid to-be returned t the reservoir space Ztl when slightly later when the cylinder 9 reaches the-lower limit ofvits travel andthe orice 21- is placed in communicatio'n with the reservoir space 420 in therfully "extended condition of the'sho-ck absorber as shown in the drawing. If the vehicle is AmoreV heavily loaded, however, the piston 9 will not movey downwardly to its full klimitiof'travel and' the additional liquid drawn in from reservoir 20 will be Vretained within Vthe System 4-5-3-23. VVThis in- Y creases the average 'working pressure applied to the'c'om-V pressed gas 2 so that compensation is madeautomatically for the increas'ed'load.Y

. The orice 17 at the top of the controlcylinder `5 is of very small cross-section. 'During very slow downwardV movement offthe Vcylinder 9, leakage through'the small orice 17 prevents liquid from beingdrawnfrom reservoir k20 through 'refill pipe' 19 and check valve 18. The

Vlppermost large ori'ce 13 in the control cylinder 5 stops the drawing of liquidV fromthe reservoir 20 as soon as it has been'passed by the check valve 12 during downward movement of the cylinder 9. As Vsoon as ythis occurs, liquid can ow freely through oriiice 14 from working Vspace 4 and the interior of .control cylinder 5 into the space 23 the intermediate cylinder 6. As stated uid into the system 4 5-8 23 to apply a suitably increased pressure to the compressed gas 2'.V When Vthe vehicle is heavily loadedor overloaded, the resilient action of the compressed Vgas 2 is augmented by engagement 4the groove 22 by-passes Ythe Vs ealingring 9a and also `tween said partitions; a control cylinder being coaxial with said main cylinder, the interior of said Vcontrol cylinder communicatingl with said working space V,derspsaid intermediate cylinder'being coaxial with said Vmain cylinder, one end of said intermediate cylinder being fixed to said xedpartition, Vsaid intermediate and main cylinders defining a reservoir space therebetween; refill pipe means having one end-in communication with said reservoir Vspace and the other end in communication with the interiorrof said intermediate cylinder adjacent to said xed partition; hydraulic fluid partially' lling said reservoir space and completely iilling the interiors of said ntermediate cylinder, said control cylinder, said movable cylinder and said working-space; urther'check valve means connected to said reiill pipe means, said further check valve means permitting fluid to ow unidirectionally from said reservoir space into the interior of said intermediateY cylinder; athird sealing means disposed at the other end of said intermediate cylinder and cooperating with the external surface of said movable cylinder, the check valve means of said secondsealing means permitting said iluid ow to unidirectionally from the interior of said intermediate cylinder into y,therinterior of said movable cylinder; means permitting restricted fluid ow Y past said iixed piston; and means placing the interior of of the flange 27 with the lower'end 'of thev compression Y V`spring 25 during therterminal portion' of the upward movement of the cylinder 9; vloA assist in the pumping Y action for load equalization, gas under pressure may advantageously be disposed in the spaceV aboveY the uid in the partiallynlled reservoir space 20.

' vIt'vyill be apparent to those skilled in the' art that various modifications may be made inthe embodiment of the Vinvention which has been herein shown and described without departing from the spirit and scope of the ventionas dened in the appended claims., 3

vWhat is claimed is:VV Y' Y l.` A shockv absorber comprising in combination; a

main cylinder closed atfone end, rsaid closed end being adaptedto be connected to the body of a wheeled vehicle; a movable'cylinder coaxial with said main cylinder and movable inwardly and outwardly of'said main cylinder,

Y said movable cylinder being closedy at its outer end and open at its inner end, said outer end being adapted toV V `from said closed end of said Vmain cylindenresilient meansyieldingly urging said partition away froni'said closed end of:said main cylinder; a iixed lpartition connected to said main cylinder and spaced from said movable partition and definingV therewith a working space besaid movable cylinder between said iixedpiston and said second sealing means in communication with said reservoir space with said movable Vcylinder substantially at its limit of outward travel. Y

2. A shock absorber according to .claim 1,'wherein said movable cylinder has an oriiice formed therein adjacent to the inner end thereof, said orifice constituting said last-named means. Y Y y .Y

3. A shock absorber according topclaim 1, wherein said movable cylinder has a longitudinalngroove formed in the external surface thereof, saidlongitudinalV groove bypassing saidrthird sealing means during theV terminal portion of Voutward movement of said movable cylinder.

4. A shock absorber according to claim` l, wherein said control cylinder has aseries of axially spaced metering 7. A shock absorber according to cl 1l, wherein said resilient means is a compressed gas. I Y Y References Cited inthe le of Vthis patent UNITED STATES PATENTS 1,855,064 Messier' VApr. 19, 1932 V1,918,698 Gruss V.. `....T. July V18, 1933 2,077,935V Johnson .V l ',Apn 20, 1937 2,348,160 Thornhill May 2, 1944 2,436,573 Heynes 1 Feb. 24, 1948 2,616,687 Butterfield Nov. 4, 1952 having one end Aconnected to said fixed partition, said control cylinder 

